Continuous transesterification process

ABSTRACT

A process for converting at least one triglyceride feedstock to at least one fatty-acid methyl ester product is disclosed. The process includes a continuous, plug-flow environment with a single-pass residence time as low as about 10 seconds, and a conversion of at least 70 percent.

RELATED APPLICATIONS

[0001] This disclosure is a continuation of a Provisional PatentApplication. No. 60/372072, filed Apr. 12, 2002, the entire disclosureof which is incorporated herein by specific reference.

TECHNICAL FIELD

[0002] Embodiments relate to a process for the continuous, plug-flowtransesterification of a plant-based oil. More particularly, embodimentsrelate to the transesterification of triglycerides to diesel fuel grademethyl esters. In particular, a continuous, plug-flow reactionenvironment is used without a phase stabilizer to transesterifiytriglycerides to their corresponding methyl esters.

BACKGROUND INFORMATION

[0003] The bio-diesel process converts fats and oils into diesel. Thisprocess includes two reactions in which the feedstock is esterified withmethanol to form methyl esters of 16 to 18 carbons in length. Thefeedstock can include free fatty acids and triglycerides with smallamounts of impurities. The purified methyl esters can be used as dieselfuel. Glycerol is formed as a byproduct of this process.

[0004] One technique for transesterification of FFAs and triglyceridesincludes a batch process. The batch process includes a two-phase liquidreaction. The two-phase liquid reaction results in long residence timesand low yields. Consequently, batch reactors need to be run at highimpeller intensity, high temperature, and high pressure to obtainreasonable reaction rates and yields.

[0005] Under atmospheric conditions, the transesterification reactioncan require many hours to proceed. A co-solvent such as tetrahydrofuran(THF) can be added to the system to substantially reduce the reactiontime by changing the two-phase liquid system into a single-phase liquid.

[0006] Other problems for bio-diesel production have a variety of, suchas long fluid hold up times, energy intensive separations, and safetyconcerns over the use of co-solvents.

[0007] What is needed is a transesterification process that avoids atleast some of the problems of the prior art.

TECHNICAL SUMMARY

[0008] A process is disclosed that operates to convert at least onetriglyceride to at least one fatty acid methyl ester in a plug-flowenvironment. The process can be accomplished in one embodiment byoperating in a temperature range from about 80° C. to about 180° C. Theprocess can also be accomplished in one embodiment by operating in aplug-flow residence time of less than three minutes. The process canalso be accomplished in one embodiment by operating in a pressureenvironment of about 30 atmospheres or less. The process limitationsresult in a conversion of the triglycerides to fatty acid methyl estersin a range from about 70 percent to in excess of about 99 percent.

[0009] The process can also include phase separation of the fatty acidmethyl esters from unreacted triglycerides and byproducts. The phaseseparation process refines the fatty acid methyl esters to a diesel fuelgrade product.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to understand the manner in which embodiments areobtained, a more particular description of various embodiments brieflydescribed above will be rendered by reference to the appended drawings.Understanding that these drawings depict only typical embodiments thatare not necessarily drawn to scale and are not therefore to beconsidered to be limiting of its scope, the embodiments will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

[0011]FIG. 1 is a schematic of a process according to an embodiment;

[0012]FIG. 2 is a schematic of a process according to an embodiment;

[0013]FIG. 3 is a schematic of a recycle process according to anembodiment; and

[0014]FIG. 4 is a process flow diagram according various embodiments.

DETAILED DESCRIPTION

[0015] The following description includes terms, such as upper, lower,first, second, etc. that are used for descriptive purposes only and arenot to be construed as limiting. Reference will now be made to thedrawings wherein like processes will be provided with like referencedesignations. In order to show the process elements of embodiments mostclearly, the drawings included herein are diagrammatic representationsof various embodiments. Thus, the actual appearance of the processes mayappear different while still incorporating the essential processes ofembodiments. Moreover, the drawings show only the processes necessary tounderstand the embodiments. Additional processes known in the art havenot been included to maintain the clarity of the drawings.

[0016] A process is disclosed that operates to convert at least onetriglyceride to at least one fatty acid methyl ester in a plug-flowenvironment. The process can be accomplished in one embodiment byoperating in a temperature range from about 80° C. to about 180° C. Theprocess can also be accomplished in on embodiment by operating in aplug-flow residence time of less than three minutes. The process canalso be accomplished in one embodiment by operating in a pressureenvironment of about 30 atmospheres or less. The process limitationsresult in a conversion of the triglycerides to fatty acid methyl estersin a range from about 70 percent to in excess of about 99 percent.

[0017] The process can also include phase separation of the fatty acidmethyl esters from unreacted triglycerides and byproducts. The phaseseparation process refines the fatty acid methyl esters to a diesel fuelgrade product.

[0018] Various plant oils can be used according to process embodiments.In one embodiment, a plant oil is used that is selected from corn oil,linseed oil, rape seed oil, combinations thereof, and the like. In oneembodiment, a plant oil is used that is selected from olive oil, palmkernel oil, coconut oil, combinations thereof, and the like. In oneembodiment, a plant oil is used that is selected from soybean oil,cottonseed oil, peanut oil, safflower oil, castor bean oil, combinationsthereof, and the like.

[0019] Other oil embodiments include oils that have a plurality ofsaturated C4-C14 contents such as coconut oil and the like. Other oilembodiments include oils that have a plurality of saturated andunsaturated C16-C18 contents such as cottonseed oil and the like. Otheroil embodiments include oils that have a majority of unsaturated C18contents such as linseed oil and the like.

[0020] Various catalysts can be used according to process embodiments.In one embodiment, a liquid-phase caustic is used. In one embodiment, acaustic such as NaOH, KOH, LiOH, and combinations thereof is used. Inone embodiment, KOH is used and the potassium in the KOH provides auseful element in the byproduct glycerol if it is used as a fertilizeror other application.

[0021] In one embodiment, an insoluble catalyst is used. In thisembodiment, a metallic compound is used. In one embodiment, the metalliccompound can be embedded upon the inner surfaces of the plug-flowreactor such that the reactants are forced across the inner surfacesunder high shear. In one embodiment where the plug-flow reactor includesa static mixing element such as packing and/or baffles, the metalliccompound catalyst can be imbedded upon the surfaces of the packingmaterial.

[0022] In one embodiment, the metallic compound is selected from tin,lead, and combinations thereof. In one embodiment, the metallic compoundis selected from mercury, cadmium, zinc, and combinations thereof. Inone embodiment, the metallic compound is selected from titanium,zirconium, hafnium, and combinations thereof. In one embodiment, themetallic compound is selected from boron, aluminum, and combinationsthereof. In one embodiment, the metallic compound is selected fromphosphorus, arsenic, antimony, bismuth, and combinations thereof. In oneembodiment, the metallic compound is selected from calcium, magnesium,strontium, and combinations thereof. In one embodiment, the metalliccompound is selected from potassium, sodium, lithium, and combinationsthereof. In one embodiment, the metallic compound is uranium.

[0023] In one embodiment, the catalyst is a combination of a causticsoluble catalyst and an insoluble catalyst.

[0024]FIG. 1 is a schematic of a process 100 according to an embodiment.A plug-flow reactor 110 including about 7 foot of ⅜ inch coiled copperpipe is provided. Reactant materials 120 include a mixture of methanol(MeOH) and a caustic catalyst including sodium hydroxide (NaOH). In oneembodiment, the reactant materials include from about 2 to about 20 gramper liter (g/L) of NaOH in MeOH. In one embodiment, the reactantmaterials include from about 5 to about 10 g/L of NaOH in MeOH. In oneembodiment, the reactant materials include about 7.5 g/L of KOH in MeOH.

[0025] The reactant materials 120 are advanced toward the plug-flowreactor 110 with a first pump 122. The first pump 122 is capable ofachieving a pressure in a range from about 1 atmosphere (atm) to about30 atm. In one embodiment, the limit pump 122 can operate against apressure of about 15 atm.

[0026] A triglyceride feedstock 130 is provided to mix with the reactantmaterials 120. The triglyceride feedstock 130 is advanced toward theplug-flow reactor 110 with a second pump 132. The second pump 132 iscapable of can operate against a pressure in a range from about 1 atm toabout 30 atm. In one embodiment, the second pump 132 can operate againsta pressure of about 15 atm.

[0027] The reactant materials 120 and the triglyceride feedstock 130 aremixed at a tec 124 before entering the plug-flow reactor 110. Bycontrolling the flow rates with the fist and second pumps 122 and 132,respectively, a residence time and a reaction pressure can be achievedaccording to various embodiments.

[0028] Example embodiments include bath temperatures for the plug-flowreactor 110 of about 50° C., about 60° C., about 65° C., about 73° C.,about 80° C., and about 87° C. After the reaction has occurred in theplug-flow reactor 110, a quench 114 accepts the product stream from theplug-flow reactor 110 to condense reaction products for analysis. Thereaction products, as condensed form a two-phase composition. Afterquenching the products, analysis of the two phases indicated the NaOHremains in the aqueous phase, along with glycerol as a byproduct as wellas unreacted methanol. Table 1 is a representation of various processesaccording to several embodiments. TABLE 1 Conversion of Triglycerides toMethyl Esters Example Residence Temperature, Conversion, No. time, s °C. percent 1 9 65 43 2 9 86.8 78 3 11.5 65 48 4 11.5 80.1 73 5 11.5 87.380 6 16 65 57 7 16 73 67 8 16 79.7 74

[0029]FIG. 2 is a schematic of a process 200 according to an embodiment.Various unit operations can be combined for a given process embodiment.Additionally, various streams are depicted according to an embodiment. Afirst reactant materials stream 1 is pumped to form a second reactantmaterials stream 2. A first triglyceride feedstock stream 3 is pumped toform a second triglyceride feedstock stream 4. Streams 2 and 4 form afirst supply stream 5 that in turn can be temperature manipulated to asecond supply stream 6. The second supply stream 6 can be furthertemperature manipulated to a third supply stream 7. Thereafter, a firstproduct stream 8 can be temperature manipulated to a second productstream 9.

[0030] In a three-phase separation process, a first light key stream 10is formed, along with a heavy key organic phase stream 14 and a heavykey aqueous phase stream 13. The first light key stream 10 can betemperature manipulated to a second light key stream 11. The secondlight key stream 11 can be further temperature manipulated to a thirdlight key stream 12. Finally, the heavy key organic phase stream 14 canbe water washed to form a washed organic phase stream 15.

[0031] Two significant unit operations include a reactor and a phaseseparator. A plug-flow reactor 210 is combined with a separation process220. The plug-flow reactor 210 is supplied from a reactant materialssource 230 and a triglyceride feedstock source 240. Product can be waterwashed at a washing process 250.

[0032] In one embodiment, the process of converting is facilitated byincluding a static mixing effect in the plug-flow reactor 210. In oneembodiment, a tube reactor is provided, which is filled with packingmaterial. The packing material causes the reactants to follow aturbulent, tortuous flow path. Examples of packing material include Pallrings, Rasching rings, Beryl saddles, inert spheres, and the like.

[0033] In one embodiment, the turbulent, continuous, plug-flowenvironment includes at least one baffle to assist in establishing aturbulent flow regime. In one embodiment, the plug-flow reactor 210 isconfigured to create a turbulent flow regime in a fluidized bed. In thisembodiment, fluidizing packing material is used. In one embodiment, asolid catalyst is used as the fluidized packing material. In oneembodiment, the solid catalyst is embedded upon the surfaces of thepacking material. In one embodiment, the solid catalyst is embedded uponthe inner surface of the plug-flow reactor 210. In either of theseembodiments, the solid catalyst can be referred to as an insolublecatalyst.

[0034] In one embodiment the continuous, plug-flow environment includesa coiled tube that operates upon high shear and optionally highoverpressure to force a quasi single-phase system to facilitate a higherreaction rate. In the coiled-tube plug-flow reactor environment, aresidence time of less than about three minutes is sufficient to achieveat least 70 percent conversion. In one embodiment, the residence time isas short as about 9 seconds and a conversion in excess of 70 percent isaccomplished. In one embodiment, a residence time of about 15 seconds isused and a conversion of greater than about 95 percent is achieved.

[0035] In one embodiment, the reactant materials source 230 and thetriglyceride feedstock source 240 each include pumping capabilities toachieve pressures between ambient pressure and up to and/or in excess ofabout 30 atmospheres according to a specific application. In oneembodiment, the process 200 operates at a pressure of about 20atmospheres or lower and the pumping capabilities of the reactantmaterials source 230 and the triglyceride feedstock source 240 are usedto supply reactants into a pressurized plug-flow reactor 210.

[0036] In operating environments that are at the lower temperature rangeherein disclosed, an overpressure can be imposed upon the reactants andproducts by use of the pumps that are part of the reactant materialssource 230 and a triglyceride feedstock source 240. In one embodiment,the overpressure is used to achieve a high shear within the plug-flowreactor 210. The high shear tends to emulsify the triglycerides and thealcohol in the front region of the plug-flow reactor 210. Another effectof the overpressure is the vapor-suppressing effect upon the alcohol. Bysuppressing the alcohol from vaporizing, it remains more available tofacilitate the transesterification reaction. In one embodiment, anoverpressure of about 20 atm is used with a temperature range from aboutambient to about 180° C. In one embodiment, an overpressure of about 10atm is used with a temperature range from about ambient to about 180° C.In one embodiment, an overpressure of about 5 atm is used with atemperature range from about ambient to about 180° C. In one embodiment,an overpressure of about 1 atm is used with a temperature range fromabout ambient to about 180° C.

[0037] In one embodiment, the triglyceride feedstock source 240 includesa warming chamber and a pump. A first feedline (stream 4) couples thetriglyceride feedstock source 240 to the reactor 210. A second feedline(stream 2) couples the reactant materials source 230 to the reactor 210.In one embodiment, the first feedline 4 and the second feedline 2 mergeto form the first supply stream 5 as depicted in FIG. 2. Where the firstsupply stream 5 is formed, mixing of the triglyceride feedstock and thealcohol can occur. Where the catalyst is a liquid-phase caustic, thecatalyst also mixes in the first supply stream 5.

[0038] The plug-flow reactor 210 is supported by various other unitoperations. A booster heater 212 acts to manipulate the second reactantstream 6 to the third reactant stream 7. Accordingly, a given feedtemperature and pressure for the third reactant stream 7 are achieved asthe third reactant stream 7 enters the plug-flow reactor 210.

[0039] The separation process 220 is supported by various other unitoperations. In one embodiment prior to products in the first productstream 8 entering the separation process 220, a booster heater 226 isused to achieve the second product stream 9. Where the separationprocess 220 is a flash unit operation, the booster heater 226 can imparta sufficient temperature to the first product stream 8 to cause thesecond product stream 9 to achieve a given separation between light andheavy keys.

[0040] Other temperature manipulation of the first light key stream 10can include an economizer 222, which can be a preheater to the firstreactant stream 5, while it cools the first light key stream 10 to thesecond light key stream 11. Additionally, the second light key stream 11can be further cooled at a light key stream cooler 224 to form the thirdlight key stream 12.

[0041] In one embodiment where the organic phase stream 14 containsentrained aqueous-type components, it can be water washed at the washingprocess 250 to form a final organic phase stream 15 that is an improvedgrade of diesel fuel methyl esters with little or no alcohol insolution.

EXAMPLE 8

[0042] Reference is again made to FIG. 2. A 7.5 g/L solution of NaOH inMeOH is supplied at a rate of 20.7 lb/min at the first reactant materialstream 4. In addition to the NaOH in MeOH, about 170 lb/min of atriglyceride stream of soybean oil is pre-warmed to about 40° C. in thefirst triglyceride feedstock stream 4.

[0043] The products exiting the plug-flow reactor 210 in the firstproduct stream 8, include about 1.7 lb/min untreated triglycerides,about 169 lb/min methyl esters, about 18.4 lb/min glycerol byproduct,and about 1.7 lb/min NaOH catalyst.

EXAMPLE 9

[0044] Reference is made to FIG. 2. In Example 9, Table 2 is a streamtable, which depicts processing conditions and results. TABLE 2Processing Conditions for Conversion of Triglycerides to Methyl EstersStream No. 1 2 3 4 5 6 7 8 T, ° F. 70 70 70 70 65 100 302 314 P, psia 25230 25 250 250 250 250 240 M, lb/hr 2,400 2,400 10,200 10,200 12,60012,600 12,600 12,600 Wt., pct Triglycerides 100 100 80.93 80.93 80.930.4 MeEsters 80.9 MeOH 95.75 95.75 18.26 18.26 18.26 9.57 NaOH 4.25 4.250.81 0.81 0.81 0.81 Glycerol 8.32 Table 2 - Continued Stream No. 9 10 1112 13 14 15 T, ° F. 356 355 320 122 355 355 n/a P, psia 240 29 29 29 2929 n/a M, lb/hr 12,600 1,460 1,460 1,460 950 10,200 n/a Wt., pctTriglycerides 0.4 3.49 3.49 3.49 0.27 MeEsters 80.9 0.45 0.45 0.45 99.7MeOH 9.57 80.57 80.57 80.57 2.32 NaOH 0.81 8.26 Glycerol 8.32 8.55 8.558.55 89.4

[0045] In one embodiment, processing conditions for Example 9 include atube as the plug-flow reactor 210. The tube is a packed pipe with aninner diameter of about 6 inch and a length in a range from about 10foot to about 30 foot. In one embodiment, the tube is about 14 foot andthe residence time is about 45 seconds. In one embodiment the tube isabout 25 foot. In one embodiment, the tube is about 14 foot andconversion of the triglyceride feedstock in stream 4 exceeds about 99.9percent according to processing conditions of the tube being a packedpipe with an inner diameter of about 6.

[0046] With reference to FIG. 2, other embodiments are disclosed.Converting is carried out in a continuous, plug-flow environment such athe plug-flow reactor 210. The plug-flow environment includes atemperature range from about 80° C. to about 180° C. The reactantmaterials pump 230 and the triglyceride feedstock pump 240 charge theplug-flow reactor 210 under conditions to cause a turbulent flow regimein the plug-flow reactor 210.

[0047] Table 3 represents other example embodiments. In examples 10-19,a 6-inch diameter, 10-foot length packed plug-flow reactor is used. Inexamples 20-30, a 0.5-inch diameter, 30-foot length coiled copper tubeplug-flow reactor is used. Additionally in examples 20-30, about 2 atmoverpressure is imposed upon the reactants and products. TABLE 3Plug-Flow Process Examples Conversion, Ex. Triglyceride Catalyst T, ° C.P, atm 1, sec pct 10 olive oil NaOH 80 2 15 >70 11 corn oil KOH 90 315 >75 12 linseed oil LiOH 100 4 15 >80 13 rapeseed NaOH 110 5 15 >85 13palm oil KOH 120 7 15 >90 14 coconut oil NaOH 130 9 35 >90 15 soybeanoil NaOH 140 11 15 >90 16 cotton seed oil KOH 150 14.5 15 >90 17 peanutoil LiOH 160 18 15 >95 18 safflower oil NaOH 170 22 15 >95 19 castor oilKOH 180 27 15 >95 20 olive oil LiOH 80 4 45 >99 21 corn oil NaOH 90 545 >99 22 linseed oil NaOH 100 6 45 >99 23 rapeseed KOH 110 7 45 >99 24palm oil NaOH 120 9 45 >99 25 coconut oil NaOH 130 11 45 >99 26 soybeanoil KOH 140 13 45 >90 27 cotton seed oil LiOH 150 16 45 >90 28 peanutoil NaOH 160 20 45 >95 29 safflower oil KOH 170 24 45 >95 30 castor oilLiOH 180 29 45 >95

[0048] Processing the triglycerides can be done at the lower end of thedisclosed temperature range to achieve a conversion of greater than orequal to about 70 percent in a single pass through the plug-flow reactor210. In one embodiment, however conversion of up to 99 percent isachieved in a single pass through the plug-flow reactor 210 byincreasing the overpressure from about 2 atm to about 15 atm. In anotherembodiment, conversion of about 99 percent is achieved in a single passthrough the plug-flow reactor by increasing the residence time. Inanother embodiment, conversion greater than 70 percent is achieved byforming a recycle stream of at least the unreacted triglycerides.

[0049]FIG. 3 is a schematic of a recycle process 300 according to anembodiment. Various unit operations can be combined for a given processembodiment. Additionally, various streams are depicted according to anembodiment. A first reactant materials stream 1 is pumped to form asecond reactant materials stream 2. A first triglyceride feedstockstream 3 is pumped to form a second triglyceride feedstock stream 4.Streams 2 and 4 form a first supply stream 5 that in turn can betemperature manipulated to a second supply stream 6. The second supplystream 6 can be further temperature manipulated to a third supply stream7. Thereafter, a first product stream 8 can be temperature manipulatedto a second product stream 9. Additionally, a first product recyclestream 8R is recycled to a reaction section of the recycle process 300.

[0050] In a three-phase separation process, a first light key stream 10is formed, along with a heavy key organic phase stream 14 and a heavykey aqueous phase stream 13. The first light key stream 10 can betemperature manipulated to a second light key stream 11. The secondlight key stream 11 can be further temperature manipulated to a thirdlight key stream 12. The heavy key organic phase stream 14 can be splitto form a heavy key organic phase recycle stream 14R. The heavy keyorganic phase recycle stream 14R is recycled to a reaction section ofthe recycle process 300. Finally, the heavy key organic phase stream 14can be water washed to form a washed organic phase stream 15.

[0051] Two significant unit operations include a recycle reactor and aphase separator, each with recycle capabilities. A plug-flow recyclereactor 310 is combined with a separation process 320. The plug-flowrecycle reactor 310 is supplied from a reactant materials source 330, atriglyceride feedstock source 340, and at least one of the first productrecycle stream 8R and the heavy key organic phase recycle stream 14R.Methyl ester product can be water washed at a washing process 350.

[0052] In one embodiment, at least one of the reactant materials source330, the triglyceride feedstock source 340, the first product recyclestream 8R, and the heavy key organic phase recycle stream 14R includespumping capabilities to achieve pressures and/or overpressures betweenambient and up to or in excess of about 30 atmospheres according to aspecific application. In one embodiment, the recycle process 300operates at a pressure of about 20 atmospheres or lower and theenumerated pumping capabilities are used to supply reactants into apressurized plug-flow recycle reactor 310.

[0053] In one embodiment, the triglyceride feedstock source 340 includesa warming chamber and a pump. A first feedline (stream 4) couples thetriglyceride feedstock source 340 to the plug flow recycle reactor 310.A second feedline (stream 2) couples the reactant materials source 330to the plug-flow recycle reactor 310. In one embodiment, the firstfeedline 4 and the second feedline 2 merge to form the first supplystream 5 as depicted in FIG. 3. Where the first supply stream 5 isformed, mixing of the triglyceride feedstock and the alcohol can occur.Where the catalyst is a liquid-phase caustic, the catalyst also mixes inthe first supply stream 5.

[0054] The plug-flow recycle reactor 310 is supported by various otherunit operations. A booster heater 312 acts to manipulate the secondreactant stream 6 to the third reactant stream 7. Accordingly, a givenfeed temperature and pressure for the third reactant stream 7 areachieved as the third reactant stream 7 enters the plug-flow recyclereactor 310.

[0055] The separation process 320 is supported by various other unitoperations. In one embodiment prior to products in the first productstream 8 entering the separation process 320, a booster heater 326 isused to achieve the second product stream 9. Where the separationprocess 320 is a flash unit operation, the booster heater 326 can imparta sufficient temperature to the first product stream 8 to cause thesecond product stream 9 to achieve a given separation between light andheavy keys.

[0056] Other temperature manipulation of the first light key stream 10can include an economizer 322, which can be a preheater to the firstreactant stream 5, while it cools the first light key stream 10 to thesecond light key stream 11. Additionally, the second light key stream 11can be further cooled at a light key stream cooler 324 to form the thirdlight key stream 12.

[0057] In one embodiment where the organic phase stream 14 containsentrained aqueous-type components, it can be water washed at the washingprocess 350 to form a final organic phase stream 15.

[0058] As illustrated, FIG. 3 depicts various recycle processes. In oneembodiment, a heavy key organic phase recycle stream 14R returnsunreacted triglycerides, along with diesel fuel-grade methyl esters, tothe plug-flow recycle reactor 310. For the heavy key organic phaserecycle stream 14R, the precise location of entry along the length ofthe plug-flow recycle reactor 310 is depicted in at an arbitrary entrypoint. In one embodiment, the location of entry is at a point ofapproximate chemical equilibrium within the plug-flow recycle reactor310 for the unreacted triglycerides and methyl esters in stream 14R. Inone embodiment, the location of entry is at a point where the unreactedtriglycerides imposes a chemical potential of reacting to form methylesters therefrom. In one embodiment, the location of entry is at a pointwhere the unreacted triglycerides are in excess of the quasi-equilibriumwithin the plug-flow recycle reactor 310.

[0059]FIG. 3 also depicts recycle of a first product recycle stream 8R,which includes aqueous, organic, and caustic catalyst if present. Forthe first product recycle stream 8R the precise location of entry alongthe length of the plug-flow recycle reactor 310 is depicted in at anarbitrary entry point. In one embodiment, the location of entry is at apoint of approximate chemical equilibrium within the plug-flow recyclereactor 310 for the unreacted triglycerides and methyl esters in stream8R. In one embodiment, the location of entry is at a point where theunreacted triglycerides imposes a chemical potential of reacting to formmethyl esters. In one embodiment, the location of entry is at a pointwhere the unreacted triglycerides are in excess of the quasi-equilibriumwithin the plug-flow recycle reactor 310.

[0060] After reacting the triglycerides, a separation of the methylesters from other stream constituents is carried out according to anembodiment. Reference is again made to FIG. 2, although separationprocessing is applicable to the process depicted in FIG. 3. In oneembodiment, the separation process 220 includes a three-phase separationthat is a flash process and an aqueous-organic settling process. In theflash process, the light key includes mostly alcohol such as MeOHaccording to an embodiment. Some glycerol byproduct also flashes as partof the light key under selected processing conditions. From Example 9,about 12 percent of the glycerol that is produced is entrained in thefirst light key stream 10. In one embodiment, the booster healer 226 isprovided to manipulate the temperature of the first product stream 8 inpreparation for the flash separation, in order to achieve above 97percent separation of alcohol into the first light key stream 10. InExample 9, about 97.6 percent of the MeOH separates from the secondproduct stream 9 in the separation process 220. In this embodiment, theMeOH flashes out of the second product stream 9, and the methyl estersseparate from the glycerol to form the respective heavy key organicphase stream 14 and the heavy key aqueous phase stream 13. According tothe processing conditions set forth in Example 9, the heavy key organicphase stream 14 is a diesel fuel grade methyl ester.

[0061] Other processing conditions can be imposed upon the separationprocess 220 to achieve a given minimum alcohol content in the heavy keyaqueous phase stream 14. In one embodiment, the separation process 220is carried out at a temperature to include no more than about 5 percentmethanol. In one embodiment, the separation process 220 is carried outat a temperature to include no more than about 1 percent methanol.

[0062] In one embodiment, however, where the presence of entrainedalcohol is not needed, a washing process 250 is carried out with a waterwash, to remove alcohol in the heavy key organic phase stream 14.

[0063]FIG. 4 is a process flow diagram 400 according to variousembodiments. At 410, the process operates to convert at least onetriglyceride to at least one fatty acid methyl ester in a plug-flowenvironment. The process at 410 is accomplished in combination with anyone of the process conditions set forth at 412, 414, and 416.

[0064] At 412, the process is accomplished by operating in a temperaturerange from about 80° C. to about 180° C. The process limitations at 410and 412 can be combined to achieve either process result of at least 70percent conversion at 420, or at least 99 percent conversion at 430.

[0065] At 414, the process is accomplished by operating in a plug-flowresidence time of less than three minutes. The process limitations at410 and 414 can be combined to achieve either process result of at least70 percent conversion at 420, or at least 99 percent conversion at 430.

[0066] At 416, the process is accomplished by operating in a pressureenvironment of about 30 atm or less. The process limitations at 410 and416 can be combined to achieve either process result of at least 70percent conversion at 420, or at least 99 percent conversion at 430.

[0067] Another embodiment includes a system. The system includesreactants, products, and processing equipment as set forth in thisdisclosure.

[0068] It can now be appreciated that the process phase of converting at410 can be combined with at least two of the process phases oftemperature limitations at 412, residence time limitations at 414, andpressure limitations at 416.

[0069] At 440, the process can add the embodiment of phase separatingthe fatty-acid methyl ester to achieve a diesel-fuel grade methyl ester.

[0070] It is emphasized that the Abstract is provided to comply with 37C.F.R. §1.72(b) requiring an Abstract that will allow the reader toquickly ascertain the nature and gist of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims.

[0071] In the foregoing Detailed Description, various features aregrouped together in a single embodiment for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments of the inventionrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter lies in lessthan all features of a single disclosed embodiment. Thus the followingclaims are hereby incorporated into the Detailed Description, with eachclaim standing on its own as a separate preferred embodiment.

[0072] It will be readily understood to those skilled in the art thatvarious other changes in the details, material, and arrangements of theport and method stages which have been described and illustrated inorder to explain the nature of this invention may be made withoutdeparting from the principles and scope of the invention as expressed inthe subjoined claims.

What is claimed is:
 1. A process comprising: converting at least onetriglyceride feedstock to at least one fatty-acid methyl ester product,wherein converting is carried out in a continuous, plug-flowenvironment, wherein the plug-flow environment includes a temperaturerange from about 80° C. to about 180° C.
 2. The process according toclaim 1, wherein converting in a continuous, plug-flow environmentincludes a static mixing effect.
 3. The process according to claim 1,wherein converting in a continuous, plug-flow environment includes astatic mixing element selected from a baffle, a packed bed, a fluidizedbed, a tortuous flow path, and combinations thereof.
 4. The processaccording to claim 1, wherein converting includes supplying a causticcatalyst and an alcohol reactant.
 5. The process according to claim 1,wherein converting achieves a conversion of the at least onetriglyceride feedstock at greater than or equal to about 70 percent. 6.The process according to claim 1 following converting, furtherincluding: separating the at least one fatty-acid methyl ester productunder conditions to achieve a diesel fuel grade methyl ester.
 7. Theprocess according to claim 1 following converting, further including:temperature manipulating the at least one fatty-acid methyl esterproduct; and flash separating the at least one fatty-acid methyl esterproduct under conditions to achieve a diesel fuel grade methyl ester,wherein flash separating is carried out at a temperature that achieves aflash separation of an alcohol between a light key and a heavy key, ofmore than about 97 percent in the light key.
 8. A process comprising:converting at least one triglyceride feedstock to at least onefatty-acid methyl ester product, wherein converting is carried out in acontinuous, plug-flow environment, wherein the plug-flow environmentincludes a pressure between about 1 atmosphere and about 20 atmospheres,and wherein converting achieves a conversion of the trigylceridefeedstock of greater than about 99 percent.
 9. The process according toclaim 8, wherein the pressure is above about 10 atmospheres, wherein thetemperature is above about 100° C., wherein converting is carried out inthe presence of an alcohol reactant, and wherein the alcohol reactant isin a sub-critical state.
 10. The process according to claim 8, whereinconverting is carried out in the presence of an alcohol reactant and acatalyst, wherein the catalyst is selected from a liquid-phase caustic,NaOH, KOH, LiOH, an insoluble, and combinations thereof.
 11. The processaccording to claim 8, wherein the pressure is above about 10atmospheres, wherein the temperature is above about 100° C., whereinconverting is carried out in the presence of an alcohol reactant and acatalyst, wherein the alcohol reactant is in a sub-critical state, andwherein the catalyst is selected from a liquid-phase caustic, NaOH, KOH,LiOH, an insoluble, and combinations thereof.
 12. A process comprising:converting at least one triglyceride feedstock to at least onefatty-acid methyl ester product, wherein converting is carried out in acontinuous, plug-flow environment, wherein the plug-flow environmentincludes a residence time of less than about 2 minutes, and whereinconverting achieves a conversion of the triglyceride feedstock ofgreater than about 99 percent.
 13. The process according to claim 12,wherein the residence time is less than or equal to about 0.75 minutes,and wherein the reactants achieve the conversion in a single-passprocess.
 14. The process according to claim 12, wherein converting iscarried out in the presence of an alcohol reactant and a catalyst,wherein the catalyst is selected from a liquid-phase caustic, NaOH, KOH,LiOH, an insoluble, and combinations thereof.
 15. The process accordingto claim 12, wherein the residence time is less than or equal to about0.75 minute, wherein the reactants achieve the conversion in asingle-pass process, and wherein converting is carried out in thepresence of an alcohol reactant and a catalyst, wherein the catalyst isselected from a liquid-phase caustic, NaOH, KOH, LiOH, an insoluble, andcombinations thereof.
 16. A process comprising: converting at least onetriglyceride feedstock to at least one fatty-acid methyl ester product,wherein converting is carried out in a continuous, plug-flowenvironment, wherein the plug-flow environment includes a residence timeof less than about 2 minutes, wherein the plug-flow environment includesa pressure between about 1 atmosphere and about 20 atmospheres, whereinthe plug-flow environment includes a temperature range from about 80° C.to about 180° C. and wherein converting achieves a conversion of thetrigylceride feedstock of greater than about 99 percent.
 17. The processaccording to claim 16, wherein the temperature is about 167° C.
 18. Theprocess according to claim 16, wherein converting is carried out in thepresence of an alcohol reactant and a catalyst, wherein the catalyst isselected from a liquid-phase caustic, NaOH, KOH, LiOH, an insoluble, andcombinations thereof.
 19. A continuous process comprising: in aplug-flow reactor, reacting an alcohol and at least one triglycerideabove ambient temperature, below about 30 atmospheres, in the presenceof an esterfication catalyst, at conditions sufficient to substantiallymaintain the methanol in a liquid phase, and at conditions to convert atleast 70 percent of the at least one triglyceride to at least one fattyacid methyl ester; and processing the at least one fatty acid methylester under conditions to achieve a diesel fuel grade thereof.
 20. Thecontinuous process according to claim 19, wherein reacting is carriedout including a reaction temperature of less than or equal to about 180°C. and a reaction pressure of less than about 20 atmospheres.
 21. Thecontinuous process according to claim 19, wherein the conditions toconvert at least 70 percent of the at least one triglyceride to at leastone fatty acid methyl ester include conditions to convert about 99percent of the triglycerides.
 22. The continuous process according toclaim 19, wherein the conditions to convert at least 70 percent of theat least one triglyceride to at least one fatty acid methyl esterinclude conditions to convert about 99 percent of the triglycerides, andinclude a single pass through the plug-flow reactor.
 23. The continuousprocess according to claim 19, wherein processing the at least one fattyacid methyl ester is carried out under conditions to separate thealcohol in a vapor phase.
 24. The continuous process according to claim19, wherein the catalyst is selected from H₂SO₄, a liquid-phase caustic,NaOH, KOH, LiOH, an insoluble, and combinations thereof.
 25. A lowtemperature, low pressure, continuous process for convertingtriglycerides to a biodiesel fuel consisting essentially of fatty acidmethyl esters of the triglycerides comprising: preheating a feed streamincluding triglycerides; continuously feeding preheated triglyceridesinto a plug-flow reactor together with methanol; continuously reactingthe methanol and the triglyceride in the presence of an esterificationcatalyst at a temperature in a range from about 80° C. to about 180° C.and at a pressure in a range from about 1 atm to about 30 atm, whereinthe pressure is sufficient to maintain the methanol in the liquid phasein the plug-flow reactor and wherein the reaction conditions and thecatalyst are effective to convert at least about 95 percent of thetriglycerides to their corresponding fatty acid methyl esters; andcontinuously recovering the fatty acid methyl esters so produced to adiesel fuel grade.
 26. The process of claim 25 wherein continuouslyreacting is done in the presence of a metallic compound as theesterification catalyst, wherein the metallic compound is selected fromtin, mercury, titanium, lead, cadmium, boron, phosphorus, calcium,magnesium, potassium, sodium, zinc, lithium, uranium, and combinationsthereof.
 27. The process of claim 25, wherein the fatty acid methylesters so produced to a diesel fuel grade have no more than about 5percent methanol.
 28. The process of claim 25, wherein the fatty acidmethyl esters so produced to a diesel fuel grade have no more than about1 percent methanol.
 29. The process of claim 25, wherein thetriglycerides have a residence time of about 0.1 minutes to about 1.5minutes in the plug-flow reactor during reaction with methanol beforerecovery as the fatty acid methyl esters so produced to a diesel fuelgrade.
 30. A system comprising: a plug-flow reaction vessel including achamber, wherein the chamber is capable of withstanding a temperaturerange from ambient to about 180° C. a pressure range from ambient toabout 30 atmospheres, and the presence of an esterification catalyst; athree phase separation vessel coupled to the plug-flow reactor vessel; acontinuous reactant charge, including: at least one triglyceride; analcohol; and a catalyst; a continuous product discharge, including: atleast one a fatty-acid alkyl ester; unreacted alcohol from thecontinuous reactant charge; and glycerol; a three-phase separationvessel discharge including a diesel fuel grade fatty-acid alkyl ester;and wherein the system operates with a single-pass configuration with aresidence time of less than or equal to about 2 minutes, and with aconversion of the at least one triglyceride in excess of about 70percent.
 31. The system of claim 30, wherein the catalyst is a metalliccompound, selected from tin, mercury, titanium, lead, cadmium, boron,phosphorus, calcium, magnesium, potassium, sodium, zinc, lithium,uranium, and combinations thereof.
 32. The system of claim 30, whereinthe catalyst is selected from a liquid-phase caustic, NaOH, KOH, LiOH,and combinations thereof.